The move is a significant one for Microsoft and its users. Before, the popular set of tools, including Word, Excel, PowerPoint and Outlook, was available only on Windows phones, which have captured a sliver of the smartphone market.
The feature is available free in Apple's App Store for subscribers to Office 365, the cloud-based version of Office's business-like tools for home users. Subscribers pay a monthly fee.
Office for iPhone is intended for people who need to edit PowerPoints or Excel spreadsheets on the go, not create them from their phones. The company said users can work with documents on their phones, and the updates will be transferred to those documents on PC versions. They'll also be able to share documents from their phones.
"When we launched Office 365 earlier this year, we committed to delivering regular updates and new capabilities to Office 365 subscribers," Julia White, general manager of Microsoft's Office division, said in a blog post. "Office Mobile for iPhone is another great example of the value of subscribing to Office 365."
The announcement comes just days after Apple announced that its own iWork productivity suite will for the first time work with Windows systems.
The Microsoft announcement serves as a counter, allowing the same kind of back-and-forth for the larger number of users who are already familiar with Office, considered by many the gold standard of productivity software.
There is no similar version of Office optimized for the iPad, which has its own more fully developed Web browser. Microsoft also did not mention whether it's developing a version for Google's Android mobile devices.
Office for iPhone is available now for users in the United States and will soon rolled out internationally, the company said.